Abstract. Measurements of submicron aerosol composition, light scattering, and size
distribution were made from 17 October to 15 November 2008 at the elevated Paposo
site (25° 0.4' S, 70° 27.01' W, 690 m a.s.l.) on the Chilean coast as
part of the VOCALS* Regional Experiment (REx). Based on the
chemical composition measurements, a receptor modeling analysis using
Positive Matrix Factorization (PMF) was carried out, yielding four broad
source categories of the aerosol mass, light scattering coefficient, and a
proxy for cloud condensation nucleus (CCN) concentration at 0.4%
supersaturation derived from the size distribution measurements assuming an
observed soluble mass fraction of 0.53. The sources resolved were biomass
burning, marine, an urban-biofuels mix and a somewhat ambiguous mix of
smelter emissions and mineral dust. The urban-biofuels mix is the most
dominant aerosol mass component (52%) followed by biomass burning
(25%), smelter/soil dust (12%) and marine (9%) sources. The average
(mean±std) submicron aerosol mass concentration, aerosol light
scattering coefficient and proxy CCN concentration were,
8.77±5.40 μg m−3, 21.9±11.0 Mm−1 and 548±210 cm−3,
respectively. Sulfate is the dominant identified submicron species
constituting roughly 40% of the dry mass (3.64±2.30 μg m−3),
although the indentified soluble species constitute only
53% of the mass. Much of the unidentified mass is likely organic in
nature. The relative importance of each aerosol source category is different
depending upon whether mass, light scattering, or CCN concentration is being
considered, indicating that the mean size of aerosols associated with each
source are different. Marine aerosols do not appear to contribute to more
than 10% to either mass, light scattering, or CCN concentration at this
site. Back trajectory cluster analysis proved consistent with the PMF source
attribution.